This invention relates to a inhalation device for administering powdered forms of medication which includes a housing with a rotatable dosing apparatus that has a circular perimeter area and is associated with defines opening of a powder reservoir located inside the housing that can be operated manually and comprises a peripheral dosing cavity for receiving a portion of powder, and a mouthpiece connected to the housing at the level of the dosing apparatus and opposing air intake holes so as to form an air duct in which the powder dose released by turning the dosing apparatus is catapulted into the user""s stream of respiratory air.
An inhalation device of this type that works without a propellant or additional air has been described, for example, in EP 0 559 663. This powder inhalator comprises a reservoir filled with a powdered form of medication that is located inside a housing, the funnel-shaped opening of which being locked by a dosing drum that can be turned manually. The perimeter of the dosing drum comprises at least one dosing cavity whose size matches the powder dose to be inhaled and which is filled with medicine whenever it is in the opening range of the powder reservoir. A mouthpiece is connected at the level of the dosing apparatus, and air intake holes are located at the opposite side of the housing. When the dosing drum is turned , the powdered form of medicine falls into the air duct of the mouthpiece, either by mere gravitational force or boosted by a vibrating mechanism, and is inhaled with the patient""s stream of inhaled air. The known problem of this device type, i.e. complete discharge of the medicine from the dosing cavity and the mouthpiece which is critical for reliable dispersing and dosing is to be achieved here by a specific air conduction system that causes puff blowing of the dosing chamber and complete inhalation of the powder dose through a short air path.
However, the inhalation devices of the type described have a disadvantage in that the medicine is not completely blown out or is not adequately dispersed in the air stream to ensure reliable dosing when the stream of inhaled air is weak only. Dosing reliability is furthermore reduced by the fact that medicine will be fed into the mouthpiece even if inhalation is weak or does not take place when the dosing apparatus is operated manually but will completely or partly remain there, so that any subsequent inhalation process will result in overdosing or multiple dosing.
To boost the stream of inhaled air, improve dispersion, and make the intake of the medicine more reliable, powder inhalators have been proposed that are equipped with a pumping device to produce an additional stream of compressed air.
For example, a defined dose of a powdered medicinal substance is placed into the flow channel of a mouthpiece located at the side of a propellant-free inhalation device as described in EP 0 549 605l using a plunger that can be moved by pressing a button inside a lateral recess forming a dosing cavity. At the same time, one interior wall of said dosing cavity is in communication with the cylinder of a pump. The preloaded plunger of the pump is released using a switching device operated by inhaling to produce an air stream which places the powdered medicinal substance via a nozzle into the stream of inhaled air and spreads it therein.
This inhalation device consists of a multitude of the most various components due to sophisticated mechanisms for dosing and for producing and releasing an additional stream of compressed air. Such inhalators are therefore very expensive as regards manufacture and assembly of their components, and they are susceptible to failure due to their complicated design and the required interaction of various elements, especially when dust, dirt, and breathing moisture can intrude. Moreover, complete- charging of the dosing cavity which forms a lateral recess cannot be guaranteed or can only be ensured by adding more components. As said additional stream of air is produced by the motion of the pump plunger and conducted to the dosing cavity via a sieve bottom, the required blowing pressure to be exerted upon the powdered medicine is either weak or requires a powerful pumping unit.
Another decisive disadvantage of this solution is the fact that the powdered form of medication is in the mouthpiece before the stream of compressed air is released in sync with respiration, and that it remains there if it is not inhaled. On the one hand, this may result in double dosage when the medicine is taken at a later point in time, on the other hand the medicinal substance lying bare can be contaminated or get moist, which would impede the operation of the powder inhalator. In addition, the known powder inhalators are not adequately protected against intrusion of dirt and moisture, especially breathing moisture, or unintentional release of the powdered form of medicine.
It is therefore the problem of this invention to provide an inhalation device of the type described above that has a simple design, allows safe handling, can be produced at low cost, and guarantees exact dosing and complete inhalation of the powdered form of medicine, thereby reliably excluding overdosing and multiple doses.
The inhalation device of the present invention includes a dosing apparatus is that connected with elastic fastening devices and includes a stop piece, and the dosing apparatus can be preloaded until it hits on a movable limit stop while the dosing cavity remains within the range of the powder dispensing hole of the powder reservoir, the limit stop being movable by the user""s breathing air for releasing the preloaded dosing apparatus. The accelerated motion of the dosing apparatus can be blocked suddenly by the stop piece.
In other words, the basic concept of this invention is to preload the dosing apparatus before the medicine is taken or before the dosing cavity containing the medicine is placed within the air duct, and that it is held in said preloaded condition to a limit stop that can be moved by inhaling. Inhaling releases and accelerates the dosing apparatus, and its accelerated motion is stopped abruptly when the stop piece of said dosing apparatus hits on the housing or housing bottom. This sudden interruption of the rotation of the dosing apparatus causes the powdered form of medication to be flung out of the dosing cavity at high speed and to be widely dispersed across the air duct. At the same time, the user""s inhalation air which caused the release of the dosing cavity and the medicine is still active so that the finely dispersed powder dose is directly carried over into the stream of the user""s respiratory air and completely taken in by the user""s body via his or her respiratory tract. As the medicine is released by respiration, it has to be inhaled. Subsequent overdosing or multiple dosing due to residual powder in the mouthpiece from a previous inhalation attempt is therefore excluded.
In accordance with another aspect of the invention said dosing cavity is designed as a dosing ball. The benefit of this design is that the air stream is swirled in the air duct which improves the dispersion of the powder.
In accordance with yet another aspect of the invention, the movable limit stop that keeps the dosing ball in a preloaded condition is attached to a trip flap that shuts the air duct and is pivotably hinged in the air duct. When the user breathes in, a negative pressure is generated that swings the trip flap and limit stop to release the rotation of the preloaded dosing ball. Moreover, said pivotable trip flap prevents the intrusion of moisture into the interior of the housing as may be caused by unintentional exhaling into the mouthpiece
An advantageous improvement of the invention comprises an operating lever for turning and preloading the dosing ball that is attached to the external side of the housing and to which a cap for sealing the mouthpiece of the inhalation device is slidably mounted on rails. Thus the cap will always be connected to the device and cannot be lost. Consequently, any risk of contamination or unintentional actuation of the arrested operating lever is either very low or completely excluded.
In accordance with another aspect of the design of the invention, a pumping device is provided in the housing whose reservoir of compressed air is in communication with the dosing cavity via a valve unit in such a way that when the preloaded dosing ball is triggered in sync with inhalation, i. e. when the powder dose is released from the powder reservoir, the valve unit will simultaneously release compressed air to the dosing cavity or to the medicine contained therein. This improves the dispersion of the powdered form of medication, especially in the early phase of deagglomeration. It also guarantees complete and reliable intake of the medicine by users with reduced respiratory capacity such as older people or children.
Other features, useful designs and benefits of the invention follow from the description of an embodiment of the invention below.